Electronic devices such as cellular phones, tablet computers and wearable devices, generally contain signal processing systems that have interfaces to the analog world. Such interfaces may include amplifiers that receive analog input signals and output amplified signals to later amplification and/or signal processing stages. The use of amplifiers typically allows for improved signal-to-noise ratio (SNR), power supply rejection ratio (PSRR) and other performance metrics of the system.
Amplifiers may be implemented discretely or may be integrated in an integrated circuit. Amplifiers may be implemented with metal-oxide-semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJT), or other transistor technologies.
As technology evolves, there has been an increase emphasis in improving power consumption while maintaining or improving other performance metrics. A typical approach for lowering power consumption has been to lower the operating voltage of the system. There are, however, physical limitations imposed by the physical characteristics of a particular device. In such lower voltage systems, allocating adequate headroom for the operation of active devices is a common design challenge.